The present invention relates to a capacity control mechanism of a scroll compressor for use in automotive air conditioning apparatus.
As a capacity-controlled type scroll compressor having a valve mechanism for opening and closing a bypass hole, there has been a configuration as disclosed in Japanese Laid-Open Patent Application No. Hei 4-179886, for example, in which a bypass hole is defined on an end plate of a fixed scroll, and a capacity control block incorporating a bypass passage enabling the bypass hole to communicate with a suction chamber formed inside the housing and a valve mechanism for opening and closing the bypass passage is constituted as a unit separate from the fixed scroll so that a high pressure introduced from a discharge cavity can be supplied to a control valve for regulating the control pressure of the valve mechanism for opening and closing the bypass hole.
As another example, there is a system as disclosed in Japanese Laid-Open Patent Application No. Hei 5-280476, in which a cylinder is provided in a fixed scroll member, into which a plunger which is capable of sequentially closing a group of bypass holes communicating between the cylinder and the compression chamber is inserted, and in which a high pressure to be supplied to a control valve for controlling the control pressure for reciprocating the plunger is introduced from nearby the front end of the innermost periphery of a vane formed on the fixed scroll.
However, in the above-described prior art configuration, as the high pressure to be supplied to the control valve is introduced from a discharge cavity, when the compressor is restarted under a state of a high discharge pressure, the high discharge pressure is applied to the control valve and the valve mechanism causing the bypass holes closed. Consequently, the compressor is started at a maximum capacity thus suffering from a large shock. On the other hand, in the latter example, although the high pressure to be supplied to the control valve is introduced from nearby the front end of the innermost periphery of the vane formed on the fixed scroll member, the configuration and machining of the lead-in passage are extremely difficult.
In the view of the above described shortcomings of the prior art, it is an object of the present invention to provide a capacity-controlled scroll compressor in which the start shock is reduced and the machinability of the fixed end plate is improved.
In order to attain the above object, the present invention provides inside a fixed end plate a control-pressure chamber which houses a control valve for controlling the controlling pressure for reciprocating a shuttle valve and a high pressure passage opening in the control chamber for introducing a high pressure to the control valve, the other end of the high pressure passage being open at a discharge hole, thereby realizing reduction of the start shock of the compressor with a simple passage structure.
Also, by forming one of the bypass holes communicating with a fluid pocket on the side wall of the discharge hole such that the bypass hole communicates with a cylinder with a straight through-hole from the outer peripheral end of the fixed end plate, or making the cylinder, the bypass hole, and the high pressure passage communicate with a straight through-hole from the outer peripheral end of the fixed end plate, it is possible to reduce the start shock of the compressor as well as to improve the machinability of the fixed end plate.
In other words, the scroll compressor of the present invention is one in which a high pressure is introduced through a passage opening at a discharge hole to a control valve for controlling the control pressure for opening and closing bypass holes with a shuttle valve.
By employing this structure, as a high pressure is instantaneously reduced to a low pressure immediately after a compressor operation has stopped, the control pressure acting on a shuttle valve is also reduced to a low pressure and the shuttle valve comes to state of opening the bypass holes. As a result, when the compressor is restarted, the start shock can be reduced as the compressor is always started at a minimum capacity. Also, the structure of the high pressure passage can be made simpler as the control-pressure chamber and the discharge hole can be made closer to each other.
The other embodiments of the present invention have one of the bypass holes formed on the side wall of the discharge hole and the bypass hole and the cylinder are made to communicate with a straight through-hole from the outer peripheral end of the fixed end plate, or the cylinder, the bypass hole formed on the side wall of the discharge hole and a high pressure passage opening at the discharge hole and introducing a high pressure to the control-pressure chamber are made to communicate with a straight through-hole from the outer peripheral end of the fixed end plate.
According to this structure, it is possible to reduce the start shock as well as to facilitate the simultaneous machining of the individual communicating holes and the passage of the fixed end plate thereby improving machinability.